Electroactive polymers are now frequently used in a number of optical and electronic applications such as in light emitting diodes ("LEDs"), photovoltaic energy converters, photodetectors, photoconductors, e.g., in electrophotography, and in chemical and biochemical sensors. In each of these applications, it may be preferred or necessary to cast multiple layers, i.e., laminates, of different polymers on a single substrate surface, so that one can achieve optimization of separate functions, for example electron or hole charge transport, luminescence, photo-induced charge generation, and charge blocking or storage.
Preparation of polymer laminates is often difficult because the initially cast or deposited layers are soluble in the solvents used for succeeding layers. In some cases, for example with polyphenylenevinylene ("PPV"), there is a suitable soluble polymeric precursor that becomes insoluble upon chemical conversion to the desired electroactive form. However, the chemical conversion process frequently involves extreme processing conditions and reactive by-products that harm the performance of the finished device. Thus, it would be desirable to have a method that permits the formation of insoluble electroactive polymer layers, but does not involve reagents or reaction conditions that would be detrimental to already existing layers.
The present invention is addressed to the aforementioned need in the art, and provides a method for preparing insoluble electroactive polymers from soluble, thermally and/or photochemically crosslinkable oligomeric precursors, without need for harsh reagents or extreme processing conditions. The invention thus represents an important advance in the art, insofar as the preparation of polymer laminates containing one or more electroactive polymer layers may now be carried out using relatively mild reagents and reaction conditions, without introduction of deleterious species or production of undesirable by-products, thus preserving the chemical and physical integrity of the materials used and the device fabricated therefrom.